Driving a Mosfet hard with low powered op amps

[dannyf]

Your design approach is flawed.

Depending on what you meant by "flawed" - pretty much all LDOs are collector- / drain-out.

[Zero999]

im not sure if i am reading this correctly or maybe my interpreting is flawed, instead of having a higher gate drive than source ... you are wanting to drive it at = or below source? yes? would lower gate turn on threshold work?

No, gate will be higher than the source but I need it to be done without using high rails for the op amps

The only way to do that is to have another voltage amplifier after the op-amp.

In short, it's not possible to do this. There are no advantages,  especially with the MOSFET you've chosen which has a high on resistance (0.85R) which will drop 1.7V at 2A. You might as well use a Darlington pair driven by a common emitter or common base amplifier. It's much simpler and effective.
http://www.vishay.com/docs/91070/91070.pdf

the image I attached was just an example taken from google images, non the less, you are right, Darlington pair will be a better solution just to avoid the hassle with Mosfets.

Good. That means the op-amp can be powered from 5V.

[dom0]

Your design approach is flawed.

Depending on what you meant by "flawed" - pretty much all LDOs are collector- / drain-out.

The design is supposed to be used in a dual supply, so it's preferable (- unless one wants to completly separate supplies, just in one casing -) to have only one additional supply for the regulator circuitry, and one central reference element (for all four (U+, I+, U-, I-) regulators). One also usually wants higher output voltages than the ops can sustain (e.g. the quoted HP has 40 V output swing and something like 50 V before the SPE. My home brew build after the schematics of it outputs 70 V and has about 100 V before the SPE. Can't do that if your op needs to reach "around" the output rails.) And you won't get that with this design.

For a single supply I'd still very much prefer the most stable configuration (i.e. emitter out).